In an engine for a leisure vehicle such as a two-wheeled motor vehicle, a three-wheeled motor vehicle, an all terrain vehicle (ATV), personal watercraft, etc., an air-intake device is mounted to supply fresh air to a combustion chamber of the engine.
A throttle valve is openably disposed in an interior of an air-intake passage of the air-intake device to control a supply amount of the fresh air. The throttle valve is moved by a throttle operation device (e.g., throttle lever, a rotatable throttle grip, and so on) configured to be hand-operated by a rider (see Japanese Laid-Open Patent Application Publication No. Hei. 1-227838).
Generally, there are two types of throttle valve drive systems, namely, mechanical drive systems and drive-by-wire systems. In mechanical drive systems, the throttle operation device is mechanically coupled to the throttle valve via a wire or a rod. In the drive-by-wire system, a controller remotely controls an actuator disposed in the vicinity of the throttle valve based on an operation signal such as an electric signal or an optical signal generated by an operation of the throttle operation device, causing the throttle valve to open and close. In some cases, the drive-by-wire system is distinguished from so-called “fly-by-light” systems, which use an optical signal as the operation signal. However in this specification, drive-by-wire systems and fly-by-light systems are treated in the same manner and collectively referred to as drive-by-wire systems.
Since a drive-by-wire system is configured in such a manner that an electronic controller generates a drive signal based on the operation signal to drive the actuator, it may also be referred to as an “electronic control throttle system.” Thus, the term “electronic control throttle system” is used through specification and claims.
Hereinafter, electronic control throttle systems will be described in detail. Upon the rider operating the throttle operation device, a sensor such as a throttle position sensor detects that the throttle operation device has been operated, and sends the detected operation signal, for example, a position signal, to an electronic controller such as an engine control unit (ECU) of the leisure vehicle through a signal line, etc. The electronic controller generates the drive signal based on the operation signal, and outputs the drive signal to the actuator to operate the actuator, causing the throttle valve of the air-intake device to open and close.
A throttle position sensor is attached to a movable member of the throttle valve of the air-intake device or a region in close proximity to the movable member. The throttle position sensor is configured to detect an open position or a closed position of the throttle valve.
Strictly speaking, the electronic control throttle system configured as described above contains a slight “deviation” associated with the control as compared to the mechanically coupled throttle system. The deviation is not substantially problematic to the rider in a high engine speed range, but makes the rider feel discomfort in a low engine speed range. For example, the deviation negatively affects responsiveness to the rider's operation just after cornering. For this reason, the leisure vehicle equipped with such an electronic control throttle system is comparatively low in responsiveness to rider control.